Heated conveyor and process for disinfecting size-reduced hospital refuse

ABSTRACT

A heated conveyor for disinfecting contaminated, size-reduced hospital refuse comprises a scraping conveyor with two endless link chains (1,2) to which drives (6) are fastened. The scraping conveyor is arranged in a housing with electricially heated floor and walls which is closed with the exception of an upper inlet opening (17), an outlet opening (19) and an air vent (18). In the disinfection process implemented by this conveyor compressed saturated steam is injected into the housing through steam nozzles.

BACKGROUND OF THE INVENTION

The invention concerns a heated conveyor and a process for disinfectingcontaminated size-reduced hospital refuse. A familiar conveyor of thiskind consists of 2 conveyor screws contrarotating in 2 open half shells,the walls of the half shells being heated with heat transfer oil. Thetwin screw conveyors are arranged inside a housing provided with aninlet opening, an outlet opening and an air vent (German Utility Model87 02 503) The use of screw conveyors has proved to be disadvantageousin operation inasmuchas the throughput capacity of such disinfectingfacilities does not come up to expectations. The material to bedisinfected is displaced laterally by the rotating movement of thespirals, causing piling-up and rendering the contact surfaces of theheated walls of the half shells ineffective. Adequate disinfection canonly be maintained if the transport velocity is kept so low that asufficiently short period of dwell can be obtained. Furthermore, the useof heat transfer oil to heat the conveyor raises environmental issues,be it the problem of the disposal of waste oil, leakages or theformation of noxious vapours during overheating.

SUMMARY OF THE INVENTION

It is, thus, the object of the invention to provide a heated conveyorand a process for disinfecting contaminated size-reduced hospital refusewith an improved disinfection performance and throughput capacity.

This object is achieved according to the invention inasmuch as theconveyor consists of a so-called scrape conveyor with two endless linkchains, to which flight attachments are secured, that the scrapeconveyor is arranged in a housing whose base and long side walls can beheated by means of electric resistance heating and which is closed withthe exception of an upper inlet opening, an exit opening and an airvent, that a drop shaft into which compressed, saturated steam can beinjected is formed by two vertical sheet metal plates and that the sheetmetal plate positioned downstream possesses an overflow opening.

The object is furthermore achieved by a process for disinfectingaccording to the invention.

The use of a scrape conveyor with rotating flight attachments,well-proven in the field of mechanical conveying and handling,eliminates the problem of the material to be handled piling up, whichcould lead to the heated contact surfaces becoming exposed. Heating thebase and the long side walls of the housing with electric resistanceheating is not only ecologically beneficial but also offers apossibility of adjusting and switching off filamanent energy quickly.

Separate regulation of the heating elements means, too, that the heatbalance within the conveyor can also be kept constant in an advantageousmanner.

The formation of a drop shaft, through which the material being fed infalls onto the base plate and the fact that the material is heated andmoistened in the drop shaft already with compressed, saturated steammeans that disinfection is begun or prepared in the drop shaft. Thesheet metal plate with its overflow opening positioned down stream ofthe drop shaft causes that part of the material in the drop shaft whichis stripped by the flight attachments of the lower belt of the linkchains and sent in the direction of the conveyor to be rotated and falldown onto the heated base plate through the overflow opening.

In the inventive process, compressed, saturated steam, free ofcondensate, is used, preferably at a temperature of 140 degrees Celsius.The temperature of the base is adjusted in an embodiment so that it isbelow that of the compressed, saturated steam being employed; thetemperature of the side walls is chosen in such a way that it is eitherat least equal to or in excess of that of the superheated steam.

The temperature at the base should preferably not exceed a range lyingbetween 119 and 125 degrees Celsius. Preference is given to the use ofsteam at 140 degrees Celsius; the temperature of the side walls in thiscase is preferably 150 degrees Celsius.

The inventive process makes periods of dwell of up to 15 minutespossible of the material to be disinfected. Shorter periods of dwell,e.g. of 10 minutes, can be attained, depending on the nature of thecontamination involved.

To ensure undisturbed movement of the link chains upon their guideways,it is expedient that the guideways of the link chains be protected byguards from hospital refuse falling onto them.

A further measure, designed to improve the efficiency of the heatedconveyor, consists, according to the invention, in the fact that aheatable intermediate plate which starts below the inlet opening andends in the area of the drop shaft, is arranged below the path of motionof the flight attachments of the upper belt of the link chains, theinlet and outlet openings lying almost on top of one another. Thissolution not only brings about the required circulation of the materialto be treated; it also causes a considerable increase in the heatedcontact surface over which the material to be treated is fed--and thatwith a scraping conveyor of the same length, by way of comparison.Additional steam nozzles can be provided above the intermediate bottom.

As hospital refuse contains on a large scale articles made of plastic,which releases harmful gaseous substances upon being heated, in order toensure that the housing is sealed as hermetically as possible it isprovided with an air vent with a filter; the driving axle of the guidewheels of the link chains nearest to the outlet opening is placedoutside the housing and sealed by glands vis-a-vis the side walls,whereas the other axle is fixed to the side walls of the housing on thefront side and the guide wheels of the axle are pivoted on the axle.

The flight attachments of the link chains preferably are provided with alayer consisting of temperature-resistant rubber or plastic, as theflight attachments drag against the wall of the base, and possiblyagainst the intermediate plate, while they are in motion.

Finally, in order to prevent heat losses, it is necessary to surroundthe housing with an outer casing, into which a thermal insulation isincorporated, this outer casing being provided with inlet and outletopenings and an air vent. It is expedient to provide the top part of theouter casing with a snap closure, so that disturbances can be removedrapidly.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing a form of construction of the subject matter of theinvention is shown by way of example.

FIG. 1 shows a vertical cross-section, a diagrammatic representation,with an outer casing providing thermal insulation, and

FIG. 2 shows a profile, in accordance with line II--II in FIG. 1,without the outer casing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

First the scrape conveyor is described, which comprises 2 endless linkchains 1, 2, which run upon guide wheels 3, 4 and carry flightattachments 6, arranged at intervals from one another, which areprovided with a coating 6a of temperature-resistant rubber. The guidewheels 3, 4 are pivotally supported on the non-driving axle 5, whosefront end is fixed by screws to the long side walls 7 of a housing,which, in addition to the short side wall 8, also possesses a base 9 anda top 10. The scraping conveyor is driven by means of an axle 11,located outside the housing in bearing brackets 12, the latter beingsupported by bracket pin 13 fixed to one of the side walls 7.

The housing, comprised of side walls 7, 8, the base 9 and the top 10, issurrounded by a outer casing 14, into which a heat insulation 15 made ofmineral wool with an aluminum-laminated coating is incorporated. The top16 of the outer casing 14 can be removed easily by means of a snapclosure (which is not shown). The top 16 of the outer casing 14 has aninlet opening 17 so that the size-reduced hospital refuse can be fedinto the appliance, a gas discharge opening 18, to which a tube with afilter (not shown) is attached and an outlet opening 19. The inletopening 17 and the outlet opening 19 lie almost on top of one another inthe case of the heatable conveyor shown in FIG. 1. It goes withoutsaying that all the openings in the outer casing 14 have correspondingopenings in top 10 and in the base 9 of the housing.

Below inlet opening 17 an intermediate bottom 20 in the shape of ashallow box-like construction begins, into which heating rods 21 of aresistance heating are installed. Below the heating rods 21, theintermediate bottom 20 contains a thermally insulating layer 22. Theintermediate bottom 20 extends between link chains 1, 2 and is securedat the upper angles 23 (FIG. 2), which are fixed to the side walls 7 ofthe housing and serve to steer the link chains 1, 2. The link chains areprotected from above by means of such angles 24, too.

The intermediate bottom 20 extends as far as the area of the fillingshaft 25, which is formed by the vertical sheet metal plates 26 and 27.The side wall 27 arranged down stream in the direction of arrow A has anoverflow opening 28 near the lower belt of the link chains 1, 2. Behindthe sheet metal plate 26 are tubes 29, which are linked up to a steamgenerating plant (not shown) and equipped with steam nozzles, whichinject the superheated steam into the drop shaft 25. A further tube 30carrying superheated steam is provided next to the sheet metal plate 27,to handle the material being transported along the base 9 in thedirection of arrow A. Base 9 and the side walls 7 are also in the shapeof a box and contain heating rods 21. Tubes 31, through which steam issent, are provided with steam nozzles above the intermediate bottom 20.

The mode of operation of the described appliance is as follows: Thesize-reduced hospital refuse is fed into the device via inlet opening 17and falls onto the heated intermediate bottom 20, onto which thematerial is fed by the flight attachments 6 of the upper belt of thelink chains 1, 2 of the scraping conveyor, which is operated extremelyslowly.

After this first treatment stage, the material falls into drop shaft 25and onto the heated base 9, where it is transported by the flightattachments in the direction of the arrow A to the outlet opening 19. Inthe drop shaft 25 the material is heated up and moistened once more, bymeans of compressed, saturated steam provided by the steam nozzles inthe tubes 29. Part of the material to be found in drop shaft 25 canoverflow via the overflow opening 28 in sheet metal plate 27 and alsofall down while rotation is being carried out, the steam nozzles of tube30 continuing to inject compressed, saturated steam. The disinfectedmaterial is led to a pressing station (which is not depicted here) viaoutlet opening 19.

In a simpler version of the device the intermediate bottom 20 is missingand the inlet opening 17 is arranged above drop shaft 25. Thesize-reduced hospital refuse arrives at the heated base 9 directly viathe drop shaft. It goes without saying that because of the arrangementof the baffles, in particular in the drop shaft 25, repeated reshufflingof the material to be treated can be achieved. Arrangements can also bemade to put steam pressure above atmospheric into service in the housingof the conveyor. In this case the waste air opening 18 must be providedwith an indicator showing excess pressure and the inlet and outletopenings 17 and 19, respectively, equipped with valves.

I claim:
 1. Heated conveyor for disinfecting contaminated, size-reducedhospital refuse, comprisinga scraping conveyor having two endless linkchains; flight attachments secured to each endless link chain; a housingin which the scraping conveyor is arranged, said housing having a top, abase and long side walls; means for electric resistance heating of saidbase and said long side walls; said housing being closed with theexception of having an upper inlet opening in the top, having an outletopening in the base and having an air vent in the top; a drop shaftbeing formed by two vertical sheet metal plates said vertical sheetmetal plates being attached to said scraping conveyor; steam nozzlespositioned within said drop shaft for injecting compressed, saturatedsteam into said drop shaft; and one of said vertical sheet metal platesbeing downstream and the other vertical sheet metal plate beingupstream, said sheet metal plate positioned upstream having an overflowopening.
 2. The heated conveyor according to claim 1,wherein said linkchains have guideways; and wherein said guideways each have a protectingcover.
 3. The heated conveyor according to claim 1,wherein a heatableintermediate bottom is positioned below a path of motion of the flightattachments of an upper belt of the link chains; said upper belt beginsbelow the upper inlet opening and ends in the area of the drop shaft;and said upper inlet opening and said outlet opening are aligned almoston top of one another.
 4. The heated conveyor according to claim 3,comprisingadditional steam nozzles provided over the heatableintermediate bottom.
 5. The heated conveyor according to claim 1,further comprisinga driving axle for guide wheels of the link chainspositioned nearest to the outlet opening; means for supporting thedriving axle outside the housing and for sealing the driving axleopposite the side walls of the housing by means of glands; another axlebeing fixed onto the sidewalls of the housing at a front end by means ofguide wheels; and said guide wheels being supported on another axle. 6.The heated conveyor according to claim 1,wherein the flight attachmentshave a temperature-resistant coating of either rubber or plastic.
 7. Theheated conveyor according to claim 1, further comprisingan outer casingfor surrounding the housing; a thermal insulation in said outer casing;and said outer casing provided with an inlet opening and an outletopening and an air vent.
 8. The heated conveyor according to claim 7,further comprisinga cover equipped with a snap closure for said outercasing.